The Droid Revolution was a threat most of the galactic public never knew existed. It was a massive revolt planned by the IG assassin droids IG-88 A, B, C, and D which never occurred as planned. Their plan was to use massive armies of droids to exterminate all the "inferior biologicals" that plagued the galaxy. They went about creating an army by implanting sleeper codes into droids that would turn on their biological masters when the IGs activated the signal. Their plot was ended with IG-88A's destruction at the Death Star II.
The IG-88s massacre their creators.
The revolution started when IG-88A was created and activated on Halowan by Holowan Laboratories during Project Phlutdroid. IG-88 realized that the Human scientists were a threat to his primary programming as an assassin droid when they tried to shut him down after realizing that his sentience programming was too powerful to control. He decided that all biological beings were inferior to droids, and then turned against his creators and killed them within seconds. He then continued to activate the other IG-88s, copying his consciousness into each, and designating them B, C, and D in order of their activation. Then, together with fellow droid IG-72, who agreed to help them get off Halowan, they escaped the facility, carving a swath of destruction along the way.
The IG-88s took off on a ship towards the foundry world of Mechis III. Their first step was to take over the world, one of the galaxy's largest droid manufacturers. They planned to use the planet's vast industrial complexes to construct a droid army for their revolution, but first they had to deal with the biological beings on the planet.
As they flew toward the planet in their ship, they simply hacked into the planet's security system, rerouted the planet's computer systems and transmitted a code to transfer their sentience into all droid minds. Before long, all of Mechis III's droid operators had sentience of their own, and were under the control of the assassin droids. It was here that the IG-88s took control of a servant droid, told it their plan, and instructed it what to do.
The droid in question was 3D-4X, a common butler droid for the head supervisor, Administrator Hekis Thun. While delivering Hekis's tea and daily report, 3D-4X pulled out a blaster pistol and shot Hekis dead, thus starting the first uprising of the Droid Revolution. The droid operatives on the planet followed their orders and rose against their biological masters, and killed all 73 on-planet Human staff within five minutes. The entire planet was now in the hands of the IG-88s, before they had ever set foot on its surface.
Their plan was to mass-produce millions of droids, with embedded sentience and then ship them out all over the galaxy. Thus, when the signal was given, all of these droids would turn on their masters. To make it seem as if nothing had occurred, the droids constructed doctored image systems, so that when Mechis III was contacted, they would think that they were talking to an organic being. To all eyes, was given the impression that biological beings were still running Mechis III. All was going well, but the IG-88's feared that soon their luck would run out, and that they might be discovered. They all agreed that they would take jobs as bounty hunters, with IG-88B as the "face" of the group, in order to lead the Imperial authorities away from their true objective.
An Arakyd Viper probe droid.
Soon, around 0 ABY, the Empire contacted Mechis III, to construct an order of Arakyd probe droids. The IG-88's took this opportunity, and implanted spy programming into the probes, so that at the same time that the probes were working for the Empire, they were spying for them. The closest the revolution ever came to getting discovered was when the Sith Lord, Darth Vader came to oversee the production of his Arakyd Vipers. However, the droids masked their presence well, and Vader merely sensed a slight disturbance.
Around 1 ABY, IG-88 reactivated a Clone Wars-era droid factory on Corellia. The former Separatist factory produced B1-Series battle droids, B2 super battle droids and droidekas until it was shut down by the Corellian Security Force. Later, IG-88 began production of droids in Nym's Factory Compound on Lok in replacement. A group of spacers attacked the compound and defeated the droid army, shutting down the factory and causing a temporary setback to IG-88's plans.
When IG-88A received information that the Empire was building a new and more powerful Death Star, he decided to upload his consciousness into the Death Star's central computer core and become the ultimate force in the universe. To do this the droids had to create a false computer core to store IG-88 in. By the time the foundries on Mechis III churned one out, IG-88B and C had been destroyed by the bounty hunter Boba Fett, and IG-88D was killed by Dash Rendar in the Ord Mantell Junkyard. IG-88A was now on his own.
He then boarded an identical shuttle to the one they would intercept which carried 100 droids disguised as stormtroopers and the computer core. The droids then intercepted the Imperial shuttle carrying the Death Star's computer core. They destroyed the escort and eventually the vessel itself. Onboard, IG-88A was surprised to find Supervisor Gurdun who had overseen Project Phlutdroid. When Gurdun told him that he should be gracious toward him, for commissioning his construction, he thanked him before planting several explosives on the vessel. Meanwhile, his mechanical stormtroopers carried the core out and downloaded its contents onto their modified core.
When the Imperials installed the core, IG-88A literally became the Death Star, with complete access and control to all systems. None of the Imperial personnel knew, although Palpatine suspected his presence when a series of doors in his throne room opened and closed wildly. The mechanical stormtroopers were scattered throughout the space station doing various things. His presence was almost revealed when one of these was crippled by a fallen crane. When the sparks coming from his legs were seen, it self-destructed, killing all the witnesses present.
IG-88 firing the second Death Star's superlaser.
When the Alliance to Restore the Republic attacked the Death Star, IG-88A fired the superlaser at the Rebel fleet, letting the Imperials believe they were in control, while he prepared to transmit his master control signal that would cause all droids to turn on their masters. However, he couldn't care less about this war between biologicals, he was only concerned with his plans, which were about to come into being. IG-88A was preparing to send out the signal to droids everywhere, when the Rebel General Lando Calrissian in the Millennium Falcon and Wedge Antilles in his X-wing, shot at the Death Star's main reactor, causing a chain reaction which destroyed the entire space station and ended IG-88A's plans for galactic conquest.